Pliny on the Well Shaft.

In the largest pyramid, there is an eighty-six cubit well inside; it is thought the river is let in by it.

There appears to be doubt as to how much the ancients knew of the interior of the Great Pyramid of Giza. In this case, there is indeed a deep shaft in the pyramid, known as the Well Shaft, which I suppose is named with reference to Pliny; as far as I can determine, it is not connected with the Nile.